Dog fennel (Eupatorium capillifolium) is generally considered non-toxic to rabbits. However, it's worth noting that rabbits have sensitive digestive systems, and individual sensitivities or reactions can vary. While there are no specific reports of toxicity associated with dog fennel in rabbits, it's always recommended to introduce new plants or herbs gradually and observe your rabbit for any adverse reactions.

If you are considering adding dog fennel or any other unfamiliar plant to your rabbit's diet or environment, it's best to consult with a veterinarian who is knowledgeable about rabbit care. They can provide specific guidance based on your rabbit's health, dietary needs, and any potential interactions or sensitivities.

Additionally, always ensure that any plants or herbs you provide to your rabbit are sourced from a safe and reliable source, free from pesticides or other harmful chemicals. When introducing new foods or plants, it's advisable to start with small quantities and monitor your rabbit for any signs of digestive upset or allergic reactions.